Why do you need electronic maps?Well I can't answer for you but for me, I play a lot by remote and need a digital image to share. I have also found that many map elements are reusable and over time I have developed I nice little library of re-usable stuff. Further more this stuff is in electronic format and so I don't have to root around looking for it on paper. So for me, electronic maps make remote gaming possible, and also have decreased my preparation time for games.
What are electronic maps?Electronic maps are simply digital images. They can be created with a wide variety of tools and many of them are free. They can be harvested from the internet (see some great links on this board). You can even take digital pictures of your own sketches on paper (I do that a lot).
How do I make them?Here to you have many options, but its fare to say have to get pretty good with a drawing program. In the beginning I used MS Paint, because it was free and already on my PC. Later I tried (and failed) to use the Gimp. I still very often sketch it up on paper and take a digital picture. Who cares how you capture the map, just do what works for you.
I would not be too worried abut how "good" the map looks, you can spend a lot of time making a detailed map, but IMO its not needed. I just want to insure the players can read it, understand the obstacles and can judge distances. Imaginations take care of the rest!
Tools to useThe GimpIt is an open source high quality image editor. It is knock off of Adobe's Photo Shop. It is powerful and to be perfectly honest, really hard to learn how to use. I still use it but I mainly use it for rudimentary things. The things I do graphically are not all that intense, and GIMP is overkill for my needs.
MS PaintIf you have windows this simplistic image editor is easy to use and requires very little time to become an expert.
MS PowerPointReally any presentation software will do the same thing for you. Basically a slide represents the game board, complete with: grid/hex, icons , map elements, tiles and notes. What I like to do is have a slide for each maps. I also have slides with useful and reusable images on them. I just copy the image i need from 1 slide and paste it into another. Furthermore the images can very quickly be: scaled and moved around. It also uses the a concept called Layers (GIMP does this as well) where you can push things behind or on top of other things. Furthermore you can set background images (master slides), typically this my grid or hex sheet. If you do not have presentation software. OpenOffice.org has one and its free. I have never used it but presumable its abilities are similar to PowerPoint's.
Ultimately I used a combination of MS Paint, GIMP and MS Power Point. I use the GIMP and Paint to edit images or create them. I use MS Power Point as map interface and image library. I use Power Point because it is very easy to layer images, scale images and move things around all in real time. IMO thats essential for real time game play. I have found to that my presentation file has grown large over time. This is because I also use it as a library, I have 100's of images that I reuse over again. Draw it once... re-use it forever!
There are also a lot of gaming map makers out there. I admit to having very limited experience with them. Most seem to be tile based, I am however happy with how I do things and have not explored any of them in depth. If anyone else has please share it!